:root{
  --bg0:#060a05;
  --bg1:#020402;
  --panel:rgba(10,16,12,.86);
  --panel2:rgba(10,16,12,.62);
  --ink:#e8ffe7;
  --muted:#a6d4a3;

  --accent:#7cff7a;
  --accent2:#00e5ff;
  --accent-rgb: 124 255 122;
  --accent2-rgb: 0 229 255;

  --border:rgba(255,255,255,.10);
  --shadow:0 24px 55px rgba(0,0,0,.45);
  --radius:20px;
}

html{
  height:100%;
  color-scheme: dark;
}

html[data-theme="nebula"]{
  --bg0:#070815;
  --bg1:#02030a;
  --ink:#eaf2ff;
  --muted:rgba(234,242,255,.72);
  --accent:#6ee7ff;
  --accent2:#a78bfa;
  --accent-rgb: 110 231 255;
  --accent2-rgb: 167 139 250;
  --panel:rgba(8,10,18,.80);
  --panel2:rgba(8,10,18,.58);
}

html[data-theme="ember"]{
  --bg0:#12060b;
  --bg1:#050208;
  --ink:#fff1f6;
  --muted:rgba(255,241,246,.72);
  --accent:#ffb86b;
  --accent2:#ff6b9a;
  --accent-rgb: 255 184 107;
  --accent2-rgb: 255 107 154;
  --panel:rgba(18,10,14,.82);
  --panel2:rgba(18,10,14,.58);
}

*{box-sizing:border-box}
html,body{height:100%}

body{
  margin:0;
  background:
    radial-gradient(950px 680px at 20% 15%, rgba(var(--accent-rgb) / .14), transparent 55%),
    radial-gradient(900px 700px at 85% 85%, rgba(var(--accent2-rgb) / .12), transparent 55%),
    linear-gradient(180deg, var(--bg0), var(--bg1));
  color:var(--ink);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  display:flex;
  align-items:center;
  justify-content:center;
}

.shell{width:min(1180px, calc(100vw - 32px))}

.topbar{
  display:flex;
  align-items:center;
  justify-content:space-between;
  margin-bottom:14px;
}
.topbar a{
  color:var(--accent);
  text-decoration:none;
  border:1px solid rgba(var(--accent-rgb) / .30);
  padding:8px 10px;
  border-radius:12px;
  background:rgba(var(--accent-rgb) / .06);
  box-shadow:0 0 0 1px rgba(0,0,0,.25) inset;
}
.topbar h1{margin:0; font-size:18px; letter-spacing:.10em; text-transform:uppercase}

.panel{
  display:grid;
  grid-template-columns: 1fr 340px;
  gap:16px;
  align-items:start;
}
@media (max-width: 980px){
  .panel{grid-template-columns: 1fr}
}

.card{
  border:1px solid var(--border);
  border-radius:var(--radius);
  background:linear-gradient(180deg, var(--panel), var(--panel2));
  padding:16px;
  box-shadow:var(--shadow);
  backdrop-filter: blur(10px);
}

.boardTop{
  display:flex;
  align-items:flex-start;
  justify-content:space-between;
  gap:12px;
  margin-bottom:12px;
}

.scores{
  display:flex;
  gap:10px;
  flex-wrap:wrap;
}

.scoreBox{
  border:1px solid rgba(255,255,255,.10);
  background:rgba(0,0,0,.18);
  border-radius:16px;
  padding:10px 12px;
  min-width:110px;
}
.scoreBox .k{
  font-size:11px;
  letter-spacing:.14em;
  text-transform:uppercase;
  color:rgba(255,255,255,.62);
}
.scoreBox .v{
  margin-top:6px;
  font-size:18px;
  font-weight:880;
  letter-spacing:.02em;
}

.controls{
  display:flex;
  gap:10px;
  flex-wrap:wrap;
  justify-content:flex-end;
}

.btn{
  appearance:none;
  border:1px solid rgba(var(--accent-rgb) / .32);
  background:
    radial-gradient(640px 220px at 20% 25%, rgba(var(--accent-rgb) / .22), transparent 60%),
    radial-gradient(640px 220px at 80% 75%, rgba(var(--accent2-rgb) / .16), transparent 60%),
    rgba(0,0,0,.18);
  color:rgba(255,255,255,.94);
  padding:11px 12px;
  border-radius:14px;
  cursor:pointer;
  font-weight:860;
  letter-spacing:.12em;
  text-transform:uppercase;
  font-size:11px;
  transition: transform .08s ease, border-color .12s ease, box-shadow .12s ease;
  user-select:none;
}
.btn:hover{
  border-color: rgba(var(--accent-rgb) / .46);
  box-shadow:0 0 0 3px rgba(var(--accent-rgb) / .10), 0 0 0 1px rgba(var(--accent-rgb) / .14) inset;
}
.btn:active{transform: translateY(1px)}
.btn:disabled{opacity:.55; cursor:not-allowed; transform:none; box-shadow:none}

.btn.secondary{
  border-color: rgba(255,255,255,.14);
  background:rgba(0,0,0,.18);
  color:rgba(255,255,255,.88);
  font-weight:780;
}
.btn.secondary:hover{
  border-color: rgba(var(--accent-rgb) / .30);
  box-shadow:0 0 0 3px rgba(var(--accent-rgb) / .08);
}

.boardWrap{
  position:relative;
  width:100%;
  max-width:620px;
  margin:0 auto;
  aspect-ratio:1/1;
  border-radius:18px;
  border:1px solid rgba(255,255,255,.10);
  background:rgba(0,0,0,.22);
  box-shadow:
    0 0 0 1px rgba(var(--accent-rgb) / .10) inset,
    0 0 38px rgba(var(--accent-rgb) / .08);
  touch-action: none;
  --n: 4;
  --gap: clamp(8px, 1.8vw, 12px);
  --pad: var(--gap);
}

.cells,
.tiles{
  position:absolute;
  inset:0;
  display:grid;
  grid-template-columns: repeat(var(--n), 1fr);
  grid-template-rows: repeat(var(--n), 1fr);
  gap: var(--gap);
  padding: var(--pad);
}

.boardWrap.noCells .cells{opacity:0}

.cell{
  border-radius:16px;
  border:1px solid rgba(255,255,255,.10);
  background:rgba(255,255,255,.04);
  box-shadow:0 0 0 1px rgba(0,0,0,.26) inset;
}

.tileWrap{
  --dx: 0;
  --dy: 0;
  transform: translate(calc(var(--dx) * (100% + var(--gap))), calc(var(--dy) * (100% + var(--gap))));
  transition: transform .14s cubic-bezier(.2,.85,.2,1);
  will-change: transform;
}

.tile{
  --c: var(--accent-rgb);
  --a: .22;
  width:100%;
  height:100%;
  border-radius:16px;
  border:1px solid rgba(var(--c) / .30);
  background:
    radial-gradient(800px 260px at 20% 25%, rgba(var(--c) / calc(var(--a) + .12)), transparent 60%),
    radial-gradient(800px 260px at 80% 75%, rgba(var(--accent2-rgb) / .10), transparent 62%),
    rgba(0,0,0,.20);
  box-shadow:
    0 0 0 1px rgba(var(--c) / .12) inset,
    0 18px 50px rgba(0,0,0,.35);
  display:flex;
  align-items:center;
  justify-content:center;
  font-weight:920;
  letter-spacing:.02em;
  color:rgba(255,255,255,.94);
  text-shadow: 0 1px 0 rgba(0,0,0,.35);
  user-select:none;
}
.tile[data-digits="1"]{font-size: clamp(22px, 5.8vw, 46px)}
.tile[data-digits="2"]{font-size: clamp(20px, 5.2vw, 40px)}
.tile[data-digits="3"]{font-size: clamp(18px, 4.6vw, 34px)}
.tile[data-digits="4"]{font-size: clamp(16px, 4.2vw, 30px)}
.tile[data-digits="5"]{font-size: clamp(14px, 3.8vw, 26px)}

.tile.new{animation: pop .12s ease-out}
.tile.merge{animation: merge .16s ease-out}
@keyframes pop{
  from{transform: scale(.86); filter: brightness(1.08)}
  to{transform: scale(1)}
}
@keyframes merge{
  0%{transform: scale(1); filter: brightness(1.08)}
  45%{transform: scale(1.08); filter: brightness(1.18)}
  100%{transform: scale(1)}
}

.overlay{
  position:absolute;
  inset:0;
  display:flex;
  align-items:center;
  justify-content:center;
  background: rgba(0,0,0,.30);
  backdrop-filter: blur(8px);
  border-radius:18px;
}
.overlayCard{
  width:min(440px, calc(100% - 28px));
  border-radius:18px;
  border:1px solid rgba(255,255,255,.12);
  background:
    radial-gradient(800px 260px at 20% 20%, rgba(var(--accent-rgb) / .18), transparent 60%),
    radial-gradient(800px 260px at 80% 70%, rgba(var(--accent2-rgb) / .14), transparent 60%),
    rgba(0,0,0,.40);
  padding:16px 16px 14px;
  box-shadow: 0 24px 70px rgba(0,0,0,.55);
}
.overlayTitle{
  font-size:18px;
  font-weight:880;
  letter-spacing:.04em;
  text-transform:uppercase;
}
.overlayText{
  margin-top:8px;
  color:var(--muted);
  line-height:1.45;
}
.overlayActions{
  margin-top:12px;
  display:flex;
  gap:10px;
  flex-wrap:wrap;
}

.hint{
  margin-top:12px;
  font-size:12px;
  color:rgba(255,255,255,.68);
  line-height:1.45;
}
.msg{
  margin-top:10px;
  min-height:18px;
  color:rgba(255,255,255,.70);
  font-size:12px;
}

.hud h2{
  margin:0 0 12px;
  font-size:14px;
  letter-spacing:.18em;
  text-transform:uppercase;
}

.settings{
  display:flex;
  flex-direction:column;
  gap:10px;
}
.row{
  display:grid;
  grid-template-columns: 1fr 1fr;
  gap:10px;
}
.field{
  display:flex;
  flex-direction:column;
  gap:7px;
}
.field label{
  font-size:11px;
  letter-spacing:.14em;
  text-transform:uppercase;
  color:rgba(255,255,255,.60);
}
.field select{
  appearance:none;
  border:1px solid rgba(255,255,255,.12);
  background:rgba(0,0,0,.20);
  color:rgba(255,255,255,.92);
  padding:10px 12px;
  border-radius:14px;
  outline:none;
}
.field select:focus{
  border-color: rgba(var(--accent-rgb) / .34);
  box-shadow: 0 0 0 3px rgba(var(--accent-rgb) / .12);
}

.checks{
  display:flex;
  flex-direction:column;
  gap:8px;
}
.check{
  display:flex;
  align-items:center;
  gap:10px;
  padding:10px 12px;
  border-radius:16px;
  border:1px solid rgba(255,255,255,.10);
  background:rgba(0,0,0,.18);
  cursor:pointer;
  user-select:none;
}
.check input{
  width:16px;
  height:16px;
  accent-color: var(--accent);
}
.check span{color:rgba(255,255,255,.86); font-size:13px}

.help{
  margin-top:12px;
  padding-top:12px;
  border-top:1px solid rgba(255,255,255,.10);
  color:rgba(255,255,255,.66);
  font-size:13px;
  line-height:1.45;
}

kbd, .kbd{
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  border:1px solid rgba(255,255,255,.12);
  padding:2px 6px;
  border-radius:8px;
  background:rgba(0,0,0,.25);
}

.hidden{display:none}

@media (max-width: 560px){
  .shell{width:calc(100vw - 24px)}
  .row{grid-template-columns: 1fr}
  .controls{width:100%; justify-content:space-between}
}

@media (prefers-reduced-motion: reduce){
  .btn{transition:none}
  .tileWrap{transition:none}
  .tile.new,.tile.merge{animation:none}
}